Glossary

Mica

Fact Sheet:
– Chemical Composition: A group of silicate minerals with varying compositions; common forms include muscovite (KAl₂(AlSi₃O₁₀)(OH)₂) and biotite (K(Mg,Fe)₃(AlSi₃O₁₀)(OH)₂)
– Hardness: 2.5 to 3 on the Mohs scale
– Crystal System: Monoclinic
– Color Varieties: Colorless, brown, green, yellow, purple, and black
– Major Localities: India, Russia, the United States, and Madagascar
– Common Uses: Insulation, cosmetics, paints, and electronics

Introduction: Mica is a versatile and widespread group of minerals known for their distinctive layered structure and excellent cleavage properties, which allow them to be split into thin, flexible sheets. These minerals play a crucial role in various ...

^MMagma

Magma is molten or semi-molten rock located beneath the Earth’s surface. It contains a mixture of liquids, gases, and crystals and can vary in composition from basaltic to rhyolitic. Magma plays a crucial role in the formation of igneous rocks through cooling and solidification and is a key component in volcanic activity.

Reference: Carmichael, I. S. E., Turner, F. J., & Verhoogen, J. (1974). “Igneous Petrology.” McGraw-Hill.

^MMagmatic Differentiation

Magmatic differentiation is the process by which a single magma evolves into multiple different types of igneous rocks through mechanisms such as fractional crystallization, assimilation, and magma mixing. This process is key to understanding the diversity of igneous rocks and the formation of complex volcanic and plutonic bodies.

Reference: Winter, J. D. (2010). “Principles of Igneous and Metamorphic Petrology.” Pearson.

^MMagnetic Anomaly

A magnetic anomaly is a variation in the Earth’s magnetic field resulting from the differing magnetic properties of subsurface rocks. These anomalies are used in geophysical exploration to detect buried structures, mineral deposits, and other geological features. Magnetic anomalies are crucial in the study of plate tectonics and the mapping of the ocean floor.

Reference: Blakely, R. J. (1995). “Potential Theory in Gravity and Magnetic Applications.” Cambridge University Press.

^MMagnetic Reversal

A magnetic reversal occurs when the Earth’s magnetic field flips, with the magnetic north and south poles switching places. These reversals are recorded in rocks and are used to study the history of the Earth’s magnetic field, plate tectonics, and the geochronology of rock sequences.

Reference: Cox, A. (1969). “Geomagnetic Reversals.” Science, 163(3873), 237-245.

^MMagnetic Susceptibility

Magnetic susceptibility is a measure of how much a material will become magnetized in an applied magnetic field. It is used in geology to study the magnetic properties of rocks, sediments, and soils, providing insights into the composition, provenance, and environmental history of geological materials.

Reference: Dunlop, D. J., & Özdemir, Ö. (1997). “Rock Magnetism: Fundamentals and Frontiers.” Cambridge University Press.

^MMagnetostratigraphy

Magnetostratigraphy is a geochronological technique that uses the magnetic properties of rock sequences to establish the age of the rocks. By comparing the recorded magnetic polarity in rock layers with the known geomagnetic polarity timescale, geologists can correlate and date sedimentary and volcanic sequences.

Reference: Opdyke, N. D., & Channell, J. E. T. (1996). “Magnetic Stratigraphy.” Academic Press.

^MManganese Crusts

Manganese crusts are hard, layered deposits rich in manganese, iron, and other metals that form on the ocean floor, particularly on seamounts and ridges. These crusts are significant for their potential as a resource for critical metals and for studying the geochemical processes of the ocean.

Reference: Hein, J. R., Koschinsky, A., & Halbach, P. (2000). “Deep-Ocean Ferromanganese Crusts and Nodules.” In: Cronan, D. S. (Ed.), Handbook of Marine Mineral Deposits. CRC Press, pp. 239-279.

^MManganese Nodules

Manganese nodules are small, rounded concretions of manganese and other metals, such as iron, copper, and nickel, found on the ocean floor. They form by the slow precipitation of metals from seawater and are significant as potential sources of rare metals and for studying oceanic geochemical processes.

Reference: Glasby, G. P. (2006). “Manganese Nodules: A Review and Global Environmental Implications.” Oceanography and Marine Biology: An Annual Review, 44(1), 1-66.

^MMantle Convection

Mantle convection is the slow, churning movement of the Earth’s mantle caused by heat from the Earth’s core. This process drives plate tectonics, influencing the movement of lithospheric plates and the formation of geological features such as mountains, mid-ocean ridges, and volcanic arcs.

Reference: Turcotte, D. L., & Schubert, G. (2002). “Geodynamics.” Cambridge University Press.

^MMantle Plume

A mantle plume is a column of hot, solid material that rises from deep within the Earth’s mantle and can lead to volcanic activity at the surface, often forming hot spots and large igneous provinces. Mantle plumes are significant in understanding the thermal dynamics of the mantle and the creation of volcanic islands like Hawaii.

Reference: Courtillot, V., & Olson, P. (2007). “Mantle Plumes and Dynamics of the Earth’s Interior.” Nature, 385(6615), 37-42.

^MMantle Transition Zone

The mantle transition zone is the region of the Earth’s mantle located between the upper and lower mantle, typically between 410 and 660 kilometers in depth. This zone is characterized by changes in mineral structure and composition, influencing mantle convection and the dynamics of plate tectonics.

Reference: Ringwood, A. E. (1991). “Phase Transformations and Their Bearing on the Constitution and Dynamics of the Mantle.” Geochimica et Cosmochimica Acta, 55(8), 2083-2110.

^MMantle Xenolith

A mantle xenolith is a fragment of the Earth’s mantle that is brought to the surface by volcanic activity, typically enclosed within an igneous rock. These xenoliths provide direct evidence of the composition, temperature, and pressure conditions in the mantle and are crucial for understanding mantle processes and Earth’s interior.

Reference: Harte, B. (2010). “Mantle Peridotites and Processes—The Kimberlite Sample.” Journal of the Geological Society, 167(4), 639-646.

^MMarine Isotope Stages (MIS)

Marine Isotope Stages (MIS) are alternating warm and cold periods in Earth’s paleoclimate, determined by oxygen isotope ratios in marine sediment cores. These stages are important for understanding past climate changes, glacial-interglacial cycles, and the timing of climatic events.

Reference: Imbrie, J., et al. (1984). “The Orbital Theory of Pleistocene Climate: Support from a Revised Chronology of the Marine δ18O Record.” In: Milankovitch and Climate. Springer, pp. 269-305.

^MMarine Regression

A marine regression occurs when sea level falls relative to the land, exposing previously submerged areas and leading to the deposition of terrestrial sediments over marine sediments. Regressions are important for understanding changes in sea level, sedimentary environments, and the stratigraphic record.

Reference: Catuneanu, O. (2006). “Principles of Sequence Stratigraphy.” Elsevier.

^MMarine Sedimentation

Marine sedimentation refers to the deposition of sediments in marine environments, including the deep sea, continental shelves, and coastal areas. The study of marine sediments provides insights into past ocean conditions, climate change, and the processes that govern sediment transport and deposition.

Reference: Kennett, J. P. (1982). “Marine Geology.” Prentice-Hall.

^MMarine Transgression

A marine transgression occurs when sea level rises relative to the land, resulting in the flooding of coastal areas and the deposition of marine sediments over terrestrial sediments. Transgressions are significant in understanding changes in sea level, sedimentary environments, and the stratigraphic record.

Reference: Catuneanu, O. (2006). “Principles of Sequence Stratigraphy.” Elsevier.

^MMass Extinction

A mass extinction is an event in which a significant percentage of all life on Earth becomes extinct over a relatively short geological time period. Mass extinctions are critical for understanding the history of life on Earth, the factors that can lead to widespread species loss, and the subsequent recovery and evolution of ecosystems.

Reference: Raup, D. M., & Sepkoski, J. J. (1982). “Mass Extinctions in the Marine Fossil Record.” Science, 215(4539), 1501-1503.

^MMass Wasting

Mass wasting is the movement of soil, rock, and debris downslope under the influence of gravity. It includes processes such as landslides, rockfalls, and soil creep. Mass wasting is significant in shaping landscapes, influencing erosion rates, and contributing to the development of valleys and other landforms.

Reference: Selby, M. J. (1993). “Hillslope Materials and Processes.” Oxford University Press.

^MMassif

A massif is a large, stable block of the Earth’s crust that is bounded by faults or flexures. Massifs are resistant to deformation and often form the core of mountain ranges. Studying massifs is important for understanding tectonic stability, the formation of mountain ranges, and the geological history of a region.

Reference: Twiss, R. J., & Moores, E. M. (2007). “Structural Geology.” W. H. Freeman.

^MMélange

A mélange is a chaotic mixture of rocks of different types and ages, often found in subduction zones and formed by the mixing of sediments, oceanic crust, and mantle material during tectonic processes. Mélanges are important in understanding the processes of subduction, accretion, and tectonic mixing.

Reference: Cowan, D. S. (1985). “Structural Styles in Mesozoic and Cenozoic Mélanges in the Western Cordillera of North America.” Geological Society of America Bulletin, 96(4), 451-462.

^MMetallogenesis

Metallogenesis is the process by which mineral deposits, particularly metal ores, form in the Earth’s crust. This process involves the concentration of metals through various geological processes, such as magmatic, hydrothermal, and sedimentary. Understanding metallogenesis is crucial for mineral exploration and the extraction of valuable resources.

Reference: Sawkins, F. J. (1990). “Metal Deposits in Relation to Plate Tectonics.” Springer.

^MMetamorphic Aureole

A metamorphic aureole is a zone of metamorphic rock that forms around an igneous intrusion due to the heat and fluids emanating from the intrusion. The study of aureoles helps geologists understand the conditions of contact metamorphism and the interactions between igneous and surrounding rocks.

Reference: Yardley, B. W. D. (1989). “An Introduction to Metamorphic Petrology.” Longman.

^MMetamorphic Core Complex

A metamorphic core complex is a large, dome-shaped structure composed of high-grade metamorphic rocks that have been exposed at the Earth’s surface through extension and thinning of the crust. These complexes provide insights into the processes of crustal extension, exhumation of deep-seated rocks, and the evolution of mountain belts.

Reference: Crittenden, M. D., Coney, P. J., & Davis, G. H. (1980). “Cordilleran Metamorphic Core Complexes.” Geological Society of America Memoir 153.

^TArchives: Glossary

Tephra is a general term for fragments of volcanic rock and ash ejected during an explosive volcanic eruption. Tephra deposits are significant in volcanology for understanding eruption dynamics, dating geological events, and reconstructing past volcanic activity.

Reference: Thorarinsson, S. (1981). “Tephra Studies and Tephrochronology: A Historical Review with Special Reference to Iceland.” Journal of Quaternary Science, 20(1), 3-21.

Rocks

Glossary

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Magma

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Magmatic Differentiation

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Magnetic Anomaly

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Magnetic Reversal

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Magnetic Susceptibility

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Magnetostratigraphy

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Manganese Crusts

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Manganese Nodules

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Mantle Convection

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Mantle Plume

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Mantle Transition Zone

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Mantle Xenolith

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Marine Isotope Stages (MIS)

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Marine Regression

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Marine Sedimentation

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Marine Transgression

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Mass Extinction

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Mass Wasting

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Massif

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Mélange

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Metallogenesis

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Metamorphic Aureole

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Metamorphic Core Complex

Mica

MMagma

MMagmatic Differentiation

MMagnetic Anomaly

MMagnetic Reversal

MMagnetic Susceptibility

MMagnetostratigraphy

MManganese Crusts

MManganese Nodules

MMantle Convection

MMantle Plume

MMantle Transition Zone

MMantle Xenolith

MMarine Isotope Stages (MIS)

MMarine Regression

MMarine Sedimentation

MMarine Transgression

MMass Extinction

MMass Wasting

MMassif

MMélange

MMetallogenesis

MMetamorphic Aureole

MMetamorphic Core Complex

TArchives: Glossary